Recent research has shown that asthma admission rates for children vary widely across geographic areas and have increased nationally for the past decade. The overall goals of this FIRST award research plan are to study three possible, but yet unproved, influences of pediatric asthma hospitalization rates - diagnostic substitution, different systems of medical care, and asthma medication use. Specific hypotheses regarding these factors will be tested in two different data sets: (1) ecologic studies of trends and area variations of the children residing in the contiguous states of Maine, New Hampshire, and Vermont for 1980 - 1994 (2) retrospective cohort analyses of children enrolled at a staff model HMO, Group Health Cooperative of Puget Sound for 1977 - 1994. These studies will utilized detailed information regarding area and individual "exposure" to differing systems of health care and asthma medications, controlling for socioeconomic status. The results from these studies will have direct relevance to the clinical care and development of public policy for children with asthma.